A senior administration official dismissed these concerns on Thursday.

“There’s been a lot of, in my judgment, hair-on-fire rhetoric on the television from the lobbyists and the politicians and the swamp creatures within the perimeter of the Beltway – and in my judgment, this is all fake news,” the official said.

The official said that concerns about increased prices for consumers due to higher costs of steel and aluminium were overblown and that no jobs would be lost at downstream manufacturers that rely on the metals.

Trump is imposing the tariffs on national-security grounds using an obscure bit of trade law. The administration argues that the US steel industry’s struggles could leave the country exposed if imports are cut off amid a geopolitical conflict.

Allies such as Canada and the European Union have called this reasoning into question, given their close political ties to the US, while the senior administration official sought to bolster it.

“The rationale from a national-security – an economic-security point of view is unassailable, and that is the underlying thing,” the official said.

The tariffs rollout has been rife with confusion and dissension in the White House. Details of the tariffs have been changing throughout the week, but here’s what they include, according to the official:

Steel imports will be hit with a 25% tariff and aluminium imports with a 10% tariff.

The measure will kick in 15 days from Thursday, on March 23.

Canada and Mexico will be exempt indefinitely. Both countries had warned of retaliatory measures if they were not exempt. So far, the Trump administration has loosely tied the exemptions to negotiations over the North American Free Trade Agreement and said a failure to renegotiate it could end the special treatment.

Other countries that present an alternative way to address the US national-security threat of their exports may be exempt as well.